Locomotive diesel engines often include turbochargers to produce higher power output, lower emissions levels, and improve efficiency. However, when a turbo charger compresses intake air and outputs charge air, the temperature of the charge air is typically higher than the temperature of the intake air. The temperature of the charge air also typically increases as locomotive throttle notch or locomotive speed increases. Generally, locomotive diesel engines are equipped with aftercoolers (i.e., a “liquid-to-air heat exchanger,” or “intercooler”) that lower the increased temperature of the charge air by transferring heat to liquids. Typically, charge air temperature is lowered by passing through an aftercooler. The temperature of the charge air as it passes through an aftercooler may be lowered by controlling the flow of coolant through the aftercooler.
Although aftercoolers typically lower charge air temperature, at low locomotive throttle notches or speeds, the temperature of the ambient air may be lower than the temperature of the coolant circulating through the aftercooler. As a result, passing charge air through an aftercooler under these conditions has the adverse effect of warming the charge air.
Prior art systems exist that enable the flow of an engine's charge air to be bypassed around an aftercooler under certain conditions. However, these bypass systems typically require additional piping to circumvent the charge air around the aftercooler. Thus, these charge air systems are typically impracticable or inefficient to include in systems with confined spatial requirements.
Other prior art systems exist that reduce or stop the flow rate of coolant to an aftercooler by reducing or stopping the flow rate of the coolant throughout a coolant loop. However, when coolant flow is reduced or stopped in these prior art systems, the coolant flow is also reduced or stopped to other components in the coolant loop, such as radiators, engines, etc.
Accordingly, there is a need to efficiently prevent the unintentional warming of charge air in a diesel engine when an engine's charge air is colder than the temperature of the coolant circulating through the aftercooler.
Other drawbacks exist.